Electromagnetic relay device



June 22, 1954 SENGEBUSCH 2,681,961

" ELECTROMAGNETIC RELAY DEVICE Filed Nov. 8, 1952 s Sheeis-Sheet 1 FIG.4

e U -10, l I E I u- I a, 3-,

INVENTOR.

HANS SENGEBUSGH ATTY.

FIG. 7

June 22, 1954 SENGEBUSC 2,681,961

' ELECTROMAGNETIC RELAY DEVICE Filed Nov. 8, 1952 3 Sheets-Sheet 2 FIG. 8

FIG 5 INVENTOR. HANS SENGEBUSCH ATTY.

June 22, 1954 SENGEBUSCH 2,681,961

ELECTROMAGNETIC RELAY DEVICE Filed Nov. 8, 1952 3 Sheets-Sheet 3 FIG. l2

FIG. ll

FIG. l0

INVENTOR. HANS SENGEBUSFH ATTY.

Patented June 22, 1954 ELECTROMAGNETIC RELAY DEVICE Hans Sengebusch, Chicago, Ill., assignor to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application November 8, 1952, Serial No. 319,508

7 Claims.

The present invention relates to electromagnetic circuit controlling devices commonly known as relays, in which a coil or winding, when energized by an electrical current, attracts an armature by means of magnetic forces induced into a soft iron structure comprising the relay mechanism, and including such armature. The armature in turn, operates a number of associated electrical contacts for controlling one or more electrical circuits. In the usual relay, the contacts remain operated only so long as the relay remains energized, and are released only when the relay becomes deenergized.

There arise occasions, however, when it is desirable to maintain the contacts operated after the associated relay has been de-energized. This may result from a need to reduce current drain, or for other reasons. In the past, this has been accomplished by (various means, such, for example, as by what is known as a polar relay, in which an auxiliary permanent magnet or the like is provided, to maintain the armature in the operated position. Such a relay, however, usually requires a two coil structure and other complications. Another arrangement provided a mechanical latching device. however, also usually required a second coil and a second armature for unlatching the contact locking mechanism.

,The main object of the present invention is the provision of a self-locking and self-unlocking relay of the latter type in which only a single coil or winding is required, and in which a simple and reliable mechanism causes the contacts to operate and lock in response to a momentary energization of the winding, and to unlock and release in response to a second momentary energization of the same winding.

Another object of the invention is the provision of a simple latching mechanism whereby, through a minor substitution of parts, the shifting of the position of the contacts will occur upon successive de-energizations of the coil, rather than on successive energizations.

Other objects and features of the invention will be made apparent by the following specification, in conjunction with the accompanying drawings, in which:

Fig. 1 is a top or plan view of one embodiment of the relay device of the invention, seen from the armature end. In this embodiment, the contacts change position on successive energizations of the coil.

Fig. 2 is a left end view, in elevation, of the relay of Fig. 1, looking toward the locking contacts.

This arrangement,

Fig. 3 is a side elevation, showing the coil, the latching mechanism, a set of locking contacts on the left, and a set of non-locking contacts on the right.

Fig. 4 is a right end View, in elevation, looking toward the non-locking contacts.

Figs. 5 to 8, inclusive, represent enlarged diagrammatic views of the latching or locking mechanism in various positions, together with the armature and stops, as they might appear in elevation in Fig. 2 if the left side of the frame were removed. Fig. 5 also shows in schematic form, how a second set of locking contacts may be controlled, in opposition to the set shown in Figs. 1, 2 and 3.

Figs. 9 to 12, inclusive, are similar to Figs. 5 to 8, and in similar manner show enlarged views in corresponding positions of a modified embodiment of Figs. 1 to 4. In this latter embodiment the position of the contacts is shifted responsive to successive de-energizations of the coil, rather than on successive energizations, as in Figs. 5 to 8.

Fig. 13 shows an enlarged left face view of the contact operating member of the latching mechanism.

Fig. 14 shows a top view of the same part of the latching mechanism shown in Fig. 13.

Fig. 15 shows a bearing pin on which the latching member of Figs. 13 and 14 is pivoted, and which cannot be seen completely in the assembly views of the relay.

With further reference to the drawings, the relay of the invention may be seen to consist primarily of a coil I, having a winding 2, terminals 3, and a magnetic-iron core 4, mounting rigidly on a magnetic iron heelpiece by means of a screw 6, and provided with a magnetic-iron armature II. On the upper end of the heelpiece 5 a nonmagnetic bearing yoke 'l is mounted, by means of a locating ring or washer 8 and a screw 9. The armature H is pivotally mounted on this bearing yoke by means of a pivot pin l0.

On the lower end of the heelpiece 5, a contact assembly l2, comprising thin metallic springs 13, carrying twin contacts of precious metal, and insulated by flat insulators such as I6, is mounted, with the aid of a retaining plate I! and. screws l8. This contact assembly is arranged to be operated by an extension [9 on the armature II, each time the armature is operated, and to be released each time the armature is released. They may be omitted if not required.

Also mounted rigidly on the heelpiece 5, by means of screws 20 (Fig. 4), is a frame 2| extending across the back of the relay as seen in into it.

Fig. 3, and having a forwardly turned section 22 at the bottom for mounting the relay, forwardly turned sections 23 and 24 at the top and center for mounting the armature restoring springs, and a forwardly turned section 25 which forms the left end or left wall of the relay opposite to the heelpiece, for mounting the locking contacts and the latching or locking mechanism.

The coiled armature restoring spring is mounted, as shown in Fig. 3, on the under side of the armature over the shank of a long screw 3| which passes through clearance holes in the armature Ii and in the forwardly turned sections 23 and 24 of the frame 2|. Immediately below the spring 38 is a tapped retaining washer 32 into which the screw 3! is turned before being inserted into the hole of the frame section 24. This washer 32 has a flat side, not visible, turned rearward against the back wall of the frame 2| to prevent its turning as the screw is threaded It will be obvious that the washer 32 holds the spring 30 in place, and that the washer and spring together hold the screw 3| in place, as well as providing back tension on the armature to hold the latter in its normal position. It will also be apparent that tightening the screw 3| will draw the washer 32 upwards, and thus add tension to the spring 30, while turning the screw 31 in the opposite direction will have the opposite effect, thus providing a ready means of adjustment. The washer 32 also acts as a lock washer, due to the pressure of the spring 30 against it, and the resultant binding action 'of the threads of the washer against the threads of the screw, which prevents self-turning.

Alsomounted on the frame extension 23, is a set screw 33 of non-magnetic material, threaded into a tapped hole in the frame, and locked by a nut 34. This set screw thus provides an adjustable armature back stop, which serves to adjust the armature stroke, or the air gap between the core of the coil and the armature, when the armature is unoperated.

At the'lower end of the forwardly bent left section'25 of the frame 2|, on the outside, a contact set 40 is mounted, by means of a retaining plate 4| and two screws 42, which thread into tapped holes in the wall section 25. The contact springs 43 of this contact set are-like those of contact. set I2, and are arranged similarly in a simple break-make formation. It will be apparent that other spring combinations, having either more springs or less, could be employed just as readily. In Fig. 2, it will be noticed also, that extra tapped holes 48 have been provided, for mounting a second contact contact set may or may not be provided, depending on requirements. It has been omitted in the .formalrviews of the relay, but is indicated sche-' matically in Fig.5.

For communicating movement from the'latching mechanism to the contact set or sets 40, 45, a U shaped cam-rider assembly is fastened, by means of its lower transverse member, to the inside wall of the wall section 25 of the frame 2|, by screws50 (Fig. 3) and 5| (Fig. 2), inserted in tappedholes inthe wall section 25. Flexible upward-extending arms 52 (Fig. 2) and 53 (Fig.

3) are formed at-the upper end into two side ears such as 54 (Figs. 3 and 5), which serve as pivots for a cam roller 55, best seen in Fig. 5. The tips of the arms 52 and 53 are so located as to communicate the movements of the latching mechanism to the contacts through insulating bushings such as the bushing 55 shown mounted on the center spring of the contact assembly 40. The contact latching mechanism is mounted between the inner face of the left wall section 25, at its upper end, and an inner bearing plate Ell (Fig. 3), mounted on the section 25 in spacedapart relation therewith by a spacer post 6| (Figs. 3 and 5), which also serves as a stop, and by a smaller'spacer post'62 (Figs. 5 and 15), which also serves as. a hearing. The post 5| is held in place by a screw 83 which passes through bearm plate Sllandpost BI and into a threaded hole in the wall section 25. The post 62, best seen in Fig. 15, is secured at its left end to the wall section 25, by insertion in a hole therein, and by a flaring operation, and at its right end'it is secured to the bearing plate EOby-the screw 66 (Fig. 3) which fits a tapped hole in that end of post 62. 1

Pivoted on the bearing-and-spacer-post -6'2 is a contact controllingrocker arm 10 which may 'be seen in Figs. 3 and 5, and is also shown in more detail in Figs. 13 and 14. Fig. 13 *shows-theleft face of the-rocker arm, that confronts thewall or section 25, and the construction of this "assembly is shown in Fig. 14, which is a top-view of Fig. 13. As clearly'shown inFig. 13, the rocker arm 10 is provided with'five projecting arms or extensions, two at the bottom which serve as stops to limit the rocking'movement, oneat each side which act as contact'controlling arms, and one at the top which serves to anchor one'end of a spring link whose function will be discussed later. staked in'openingsin the side extensions of the rocker arm are studs II and 12 (Fig. 14)

which serve'as pivotsfor two operating pawls yet to be described. staked in a larger opening in the center of the rocker arm 10 isa hollow stud 13 which fits over the post 62 "to provideabearing or pivot for the rocker arm. Grooves such as around the circumference of'thestuds ll, '12 and '13 provide a nest for'a semi-circular 'or arcuate spring 18, best seen in Fig. 5, which serves to hold the operating pawls inplace 'on'the studs 1| and 12, and also provides a'certainamount of operating tension.

The operating pawls or rocking pawls consist of a pawl and a pawl 8|, the lower ends "of which are pivoted on the studs II and 12 of the rocker armlll, and the upper ends of which are in juxtaposed relation, below theworking tip of the armature II. The lowerends are held in place on the studs against the back of the rocker arm 10, by the ends of the spring 18, as previously indicated. The upper ends '(if the pawls and BI have forwardly bent sections 82 and 83 (Fig. 5 along the inner juxtaposed edges, which form rubbing surfaces which facilitate the shifting of the position of these pawls which takes place bothzlongitudinally and laterally, as the relay is caused to operate and release. The

longitudinal shifting of the pawls is limited vby 3). These stop studs havethreaded endssmaller in diameter than the shank for 'turningiinto means.

1 spring 38.

wire pivot 92, the long arm of which passes through the hole in the hub 9| and a small hearing hole in the wall 60, while the short arm is snapped into place in a vertical slot in the wall 25, as best seen in Fig. 3.

The rocker arm 90 is provided with two upward extending arms 93 and 94 disposed on either side of the forwardly bent extensions 82 and 83,

to provide the means for controlling the previously mentioned lateral shifting movement of the pawls 8|! and 8|, The pivotal movements of the rocker arm 90 are controlled, in turn, by the movements of the rocker arm 18, through the medium of a U shaped spring 95, which is inserted in holes in the adjacent edges of the two rocker arms, and forms a spring link joining the two in such a way that the upper rocker arm is urged to take up a position corresponding to that of the lower rocker arm.

The operation of the latching mechanism can best be seen with reference to Figs. 5 to 8, which show successive positions of the armature II. and of the various elements of the latching The contact springs, shown in Fig. 5, are indicated in schematic form, to facilitate following the operation. Actually, as shown in Figs. 1 to 3, the contact springs are mounted in front -of the rocker arm 19 and parallel therewith,

while the cam follower roller or rollers, are arof the rocker arm 10, rather than on their edges as shown in Fig. 5.

In Fig. 5 it will be seen that the armature II is in the normal or unoperated position, the pawls 8|] and BI and the rocker arms 90 and 10 have all been shifted to the left, with the right pawl 8| aligned with the working tip of the armature H, and shifted longitudinally upward, while the pawl 80 has been shifted longitudinally downward. The right arm 94 of the rocker arm 99 is held against the right pawl 8| by the tension of the spring link 95 which is urging the bottom of the rocker arm 90 to the right, and consequently urges the upper part of the rocker arm 90 to the left. The arm 94 in turn urges the pawls 80 and 8| also to the left. Further leftward movement of the rocker arm 90 and the pawls 80 and 8| is prevented by the stop 84, while further leftward or anticlockwise movement of the rocker arm 10 is prevented by the stop 6| In this position of the rocker arm 10, the contact set 40 as shown in Figs. 3 and 5, is in the normal or unoperated position. The opposing contact set 45, shown only in Fig. 5, will, if used, be in the operated position as indicated.

In Fig. 6, in response to energization of the coil of Fig. 3, the armature H has been pulled downward to the operated position against the core of the coil, and compresses the restoring As it moves downward, the armature H strikes against the top of the pawl 8| and forces it downward. As the pawl 8| moves downward, the rocker arm 20 is turned or rocked in a stop 5|, as shown. The movement of the rocker arm I0 in turn, causes the pawl to move upward, to the position indicated. The movement of the rocker arm 10 also compresses the spring 95, and reverses the relative position of the pivot points thereof. The spring link 95 now urges the lower part of the rocker arm to the left,

and tends to turn this rocker arm in a clockwise direction against the left face of the extension 82 of the pawl 8!]. Lateral movement of the pawls 80 and BI is prevented however, at this time, by the downward pressure of the armature The rocker arm 10, in the position shown in Fig. 6, will obviously cause the contact set 40 to be operated, and the contact set 45, if used, to be released.

In Fig. '7, in response to the subsequent deenergization of the coil the armature I has been moved upward again to its normal position, by the upward pressure of the restoring spring 30 of Fig. 3. The upper rocker arm 90 isnow free to move in response to the urging of the spring 95, and rocker arm 98 is accordingly turned in a clockwise direction, and forces the pawls 89 and 8| over to the right against the stop 85. In this position, the pawl 80, rather than the pawl 8| is aligned with the working tip of the armature The lower rocker arm 10 is unaffected by the release, and the contact set '40 will remain operated, and the set 45, if used, will remain released.

In Fig. 8, in response to the next energization of the relay coil, the armature II has again moved downward to the operated position. As it moves downward, the armature [I now strikes against the top of the pawl 80, forcing the latter downward. The pawl '19 is thereby rocked anticlockwise until again stopped by the stop 6|, and moves the pawl 8| upward to the position indicated. The movement of the rocker arm 10 again compresses the spring link 95, and again reverses the relative position of its pivot points. The spring now urges the lower part of the rocker arm 99 to the right and tends to turn this rocker arm in an anti-clockwise direction against the right face of the extension 83 of the pawl 8|. Lateral movement of the pawls and Bi is again prevented however, at this time, due to the interference of the armature The rocker arm in, being now in the position of Fig. 5, will cause the contact set 4|] to be released, and the contact set 45, if used, to be operated, as shown in Fig. 5.

In response to the next de-energization of the coil of the relay, the armature II will again be moved upward to the normal position by the spring 30. The upper rocker arm 9|) and the pawls 80 and 8| are now free to move laterally, and are accordingly turned in an anti-clockwise direction by the spring 95, until stopped by the stop 84. A complete cycle of operations has thus been completed, and all of the elements of the latching mechanism are again in the positions shown in Fig. 5.

With reference to the alternative form or embodiment of the invention as covered by Figs. 9 to 12, it is only required to change the form of the two pawls to the form shown in Fig. 9 and to use an armature with two working tips disposed on either side of the pawls as also shown in Fig. 9, and a hollow space in lieu of the central working tip of armature Otherwise the new armature III is identical with the armature shown in Figs. 1 and 3. The new pawls I88 and |8| are also very similar to the pawls 80 and BI exceptfor the use of outward- 1yextending shoulders I 32' and l 83 arranged to be engaged in turn by theworking tips of the ..armature I l l on successive releases of this armaiture. Since the working tips of the armature il'llralsoserveas stops, the stops 84 and 85are :nolonger required and are therefore omitted.

The. operation of Figs. 9 to 12is similar to the :operation of Figs. 5 to 8 except that the rocker farm changes'positionzonly in responseto the .:release of the'armature, while the rocker arm EQULIGVBISGS the lateral position of the-pawls: only ainzresponse to the operation of thearmature.

In Fig. 9 for example, the armature Hi is in ..its:,upper or unoperated'position, and thezpawls I80 and NH are shown shifted laterallyito the rightgalong with the'upperrocker arm 90. The contact-controlling lower rocker arm 10 is in its .anti-iclockwiseposition, as in Fig. 5. In this po- .;sition of the rocker arms 10 and 99, thespring .link 95 is compressed, and its angular position is such that it tends to force the upper rocker arm-90 .to move inan anti-clockwise direction. .zBecause of the interference of the armature lll ;how,ever,.the paw1s I80 and IBI are prevented from moving to the left, and thus the movement of the rocker arm 90 is also prevented, .or very .greatly limited. The contacts will also be in :the position shown in Fig. 5.

.In-Fig. 10, in response to the energization of the coil of the relay, the armature 1 H has been drawn downward to its operated position. In this position, the armature HI frees thepawls 180 and NH, and the upper rocker arm 90 is eniabled to turn anticlockwise, and move the pawls lto theleft under control of the spring 95. The .shoulder 182 of the pawl I86 now passes over the left working tip of the armature HI, and .becomes aligned therewith in preparation for the release. The same left Working tip of the armature also limits'the leftward movement of the pawls, in obvious manner.

In Fig. 11, in response to the subsequent de- .energization of the coil, the armature III has been moved upward again to itsnormal position .by the restoring springof Fig. 3. As a result .of this movement, the pawl {80 is lifted to the ,positionishown, by the left tip of the armature. .As the pawllBfl moves upward, the lower rocker .arm .10 ,is rocked in a clockwise direction until i-blockedfrom further movement by the stop 6|. lThismovement of the rocker arm 10 in turn pulls the pawl l8l downward to the position shown. .Themovement of the rocker arm Til also com- ,pressesthe spring 95 and reverses the angular ,position thereof. The spring link 95 now urges thelowerpart of the rocker arm 90 to the left, and tends to turn this rocker arm in a .clockiwise direction, and thus, move the pawls I80 and l8l to the right. The pawls [80 and NH. are prevented from moving laterally however, by the :armature I II and the pawls in turn prevent-any "considerable movement of the rocker arm 90. As "a result of the movement of the lower rocker arm 10 however, the contact set 40 willbe operated, and-the contact set 45, if furnished, will be released.

'In Fig. 12;in"resp0nse to the next energization of the coil l,the armature III has again been drawn downward by the induced magnetic forces, "to "its'operated-position. In this position, the

"armature has-pulled clear of the pawls I80 and "IN, whereupon the upper rocker arm 90 isenabledto turn in a clockwise direction and move the pawls to the right under control of the spring dink-"95. The shoulder 1830f the pawl l8! now "passes-over the right working tip ofthe armatipof the armature.

again stopped by stop 6!.

ture Ill, in readiness to bemovedupward thereby uponthe next release. The right working 'tip of the armature also serves to limittherightward movement of the pawls.

In response to the nextde-energization. of -the relay coil, the armature HI will again be:forced upwardto its normal position by the action of the armature restoring spring'30. As a result: of

this movement, the :pawl [81 is lifted again 'to the position shownin Fig. 9 by the right working The pawl IBI in turn,=rocks the lower rocker arm "Hi anti-clockwise until .it is The rocker arm "10 pulls the pawl 18!! downward to the :position shown in Fig. 9, and shifts and oompressesthe spring link 95, which now tends to turn the upper rocker arm 98 anticlockwise, and thus move the pawls I and l8l back to the1le'ft. The lateral movement of the pawls is prevented however, by the armature Ill, and the pawlsin turn hold back the rocker arm 90. The contact set 40 is now again released and the contact set 45, if used, is now operated. A complete cycle of operations has accordingly been completed andall of theeleinents are again in thepositions shown in Fig. 9.

What is claimed is:

1. In a relay or circuit'controlling device mcluding an armatureand means for movingitga first rocker arm having two normal positions, a pair of pawls each .having one end connected to movement of said armature in its other direction for reversing the position of said second rocker arm, means responsive to saidmovement of said second rocker 'arm'for reversing the lateral position ofgsaid pawls, means includingtheiother of said pawls responsive to a secondmovement l of said armaturein said one direction for moving said firstrocker arm back to its originaLposi- .tion, said spring link means responsive to said last-movement of said first rocker arm-and-to-a .second-movementiof said armature-in its other direction for restoring said second 'rockerwarm :to its .originalposition, means .responsivevto said last' movement of said second rocker arm for restoring said pawls-to their original position, and'contacts operated by said first rocker-arm on :one of its said movements and released on "the other.

.ZJII]. arelay or circuitcontrollingdevice asiin :claim 1.1,rextensions on said first :rocker garm, :two spring contact assemblies respectively operable by said extensions, and means including said extensions for operating one of said spring contact assemblies andreleasing the other in one :position of said first rocker arm, and for releasing said-one assembly andoperating the other as- .[Sfil'IlblY inthe otherposition of said rocker-arm.

3. In a relay i device comprising an :armature pawls engaged and operated by said armature responsive to a given operation thereof for rocking said rocker arm to one of its said positions, a second rocker arm adjacent said first rocker arm and also having two normal positions, a spring link connecting adjacent edges of said rocker arms, said spring link jointly responsive to said movement of said first rocker arm and the subsequent release of said armature for rocking said second rocker arm to a given one of its said positions, means responsive to said movement of said second rocker arm for moving the free ends of said pawls to one of their said posi tions, the other of said pawls engaged and opereted by said armature responsive to the next op"- eration of said armature for rocking said first rocker arm to the other of its two positions, said spring link jointly responsive to said last movement of said first rocker arm and the subsequent release of said armature by rocking said second rocker arm to the other of its two positions, means responsive to said last movement of said second rocker arm for moving said pawls to the other of their two positions, and contacts operated by said first rocker arm in said one position and released thereby in said other position.

i. In a relay device as in claim 3, first, second, and third contact assemblies, an extension on said armature, means including said extension for operating said first contact assembly on each operation of said armature and for releasing said assembly on each release of said armature, a pair of extensions on said first rocker arm, and

means including said last named extensions for operating said second contact assembly and releasing the third on one operation of said armature, and for operating said third contact assembly and releasing the secondon the next succeeding operation of said armature.

5. In a relay device including a contact set, a first rocker arm, an extension on said rocker arm for operating said contact set in one position of said arm and for releasing it in the opposite position of said arm, an armature with means for operating and releasing it, two rocking pawls each having one end pivoted on said rocker arm, a second rocker arm, means controlled by said second rocker arm for holding said rocking pawls in one or the other of two operating positions with relation to said armature, one of said pawls operated by said armature responsive to a first operation thereof for reversing the position of said first rocker arm, a rocker-arm interlinking means actuated in response to said movement of said first rocker arm and the first release of said armature for reversing the position of said second rocker arm and said pawls, the other of said pawls then operated by said armature responsive to a second operation thereof for returning said first rocker arm to its original position, and said interlinking means actuated in response to said last movement of said first rocker arm and a second release of said armature for returning said second rocker arm and said pawls to their original positions.

6. In combination in a relay device including an armature and a contact set, means for operating said armature and means for releasing it, a first rocker arm having two extreme positions, a pair of pawls each having one end pivoted on said rocker arm and the other ends free adjacent said armature, said free ends having two extreme positions each placing a different one of said pawls in the release path of said armature, a second rocker arm adjacent said first rocker arm and also having two extreme positions, a spring link connecting adjacent sides of said rocker arms, said second rocker arm rotated to a given one of its said positions by said link under control of said first rocker arm responsive to a given operation of said armature, means responsive to said rotation for moving said free ends of said pawls to a given one of their said positions, one of said pawls engaged and operated by said armature responsive to the following release thereof for rotating said first rocker arm to a given one of its said positions, means responsive to said last rotation for operating said contact assembly, said second rocker arm rotated to the other of its said positions by said link under control of said first rocker arm responsive to the next succeeding operation of said armature, means responsive to said last rotation for moving said free ends of said pawls to the other of their said positions, the other of said pawls engaged and operated by said armature responsive to the next succeeding release thereof for rotating said first rocker arm to the other of its said positions, and said contact operating means responsive to said last rotation for releasing said contact assembly.

7. In a relay device including a contact set, a first rocker arm, an extension on said rocker arm for operating said contact set in one position of said arm and for releasing it in the opposite position, an armature, means for operating and releasing said armature, two rocking pawls each having one end pivoted on said rocker arm, a second rocker arm, means controlled by said second rocker arm for moving said pawls to one or the other of two operating positions with relation to said armature, a rocker-arm interlinking means actuated in accordance with the position 01 said first rocker arm and in response to a first operation of said armature for reversing the position of said second rocker arm and said pawls, means for operating one of said pawls responsive to the first release of said armature for reversing the position of said first rocker arm, said interlinking means actuated in accordance with the new position of said first rocker arm and in response to a second operation of said armature for returning said second rocker arm and said pawls to their original positions, and means for operating the other of said pawls responsive to a second release of said armature for returning said first rocker arm to its original position.

References Cited in the file of this patent UNITED STATES PATENTS Number 

